When you run into problems with DNS, the Nslookup utility is the tool of choice for tracking down problems. Nslookup enables you to perform selective zone transfers so that you can examine resource records in the zone. You can also use Nslookup to verify that a DNS server exists, find out what zone it manages, verify that the DNS server has a particular resource record, and browse the resource records as if you were browsing a directory.
Nslookup has two modes: Interactive and Non-Interactive. If you run Nslookup and specify parameters on the command line, you run the utility in Non-Interactive mode. To see the IP address for www.guam.net and the name servers that are authoritative for the zone that holds the A